Should baseline laboratory tests be obtained for every patient before starting an antipsychotic medication?

Should You Get Baseline Labs on Everyone Starting an Antipsychotic?

Yes, you should obtain comprehensive baseline laboratory testing before initiating any antipsychotic medication in all patients. 1

Required Baseline Laboratory Assessment

Before starting antipsychotic treatment, obtain the following measures for every patient 1:

• Body mass index (BMI) and waist circumference 1
• Blood pressure 1
• HbA1c and fasting glucose (or random glucose if fasting sample cannot be obtained initially, followed by fasting measure if abnormal) 1
• Fasting lipid panel (total cholesterol, LDL, HDL, triglycerides) 1
• Prolactin level 1
• Liver function tests (ALT, AST) 1
• Urea and electrolytes (BUN, creatinine) 1
• Full blood count 1
• Electrocardiogram 1
• Pregnancy test in females of childbearing age 1, 2

Evidence-Based Rationale

The 2025 INTEGRATE guidelines from The Lancet Psychiatry provide the most current, high-quality recommendation that baseline metabolic and cardiovascular assessment is mandatory before antipsychotic initiation 1. This comprehensive baseline serves three critical functions: it identifies patients at elevated risk for metabolic complications, establishes reference values for future monitoring, and documents pre-existing abnormalities that might otherwise be misattributed to medication effects 1.

Antipsychotic medications—particularly olanzapine, clozapine, quetiapine, and risperidone—carry substantial risk for weight gain, diabetes, dyslipidemia, and cardiovascular complications 1. Without baseline documentation, you cannot distinguish medication-induced metabolic changes from pre-existing conditions, which creates both clinical and medicolegal vulnerability 1.

Follow-Up Monitoring Schedule

After obtaining baseline labs, implement this monitoring schedule 1:

• Weeks 1-6: Check BMI, waist circumference, and blood pressure weekly 1
• Week 4: Repeat fasting glucose 1
• Month 3: Repeat all baseline measures (BMI, waist circumference, blood pressure, HbA1c, glucose, lipids, prolactin, liver function, renal function, full blood count) 1
• Annually thereafter: Repeat comprehensive metabolic panel 1

Medication-Specific Considerations

For Clozapine

Clozapine requires additional mandatory hematologic monitoring due to agranulocytosis risk 3:

• Baseline: White blood cell count must be ≥3,500/mm³ with no history of myeloproliferative disorder or prior agranulocytosis 3
• Weeks 1-26: Weekly complete blood count with differential 3
• Weeks 27-52: Biweekly complete blood count 3
• After 12 months: Monthly complete blood count for duration of therapy 3
• Post-discontinuation: Continue monitoring for 4 weeks after stopping clozapine 3

For Haloperidol and First-Generation Antipsychotics

Add baseline and periodic assessment for 2:

• Extrapyramidal symptoms (including tardive dyskinesia screening) 2
• QTc interval monitoring via ECG, especially in patients with cardiovascular risk factors 2

Common Pitfalls to Avoid

Do not delay antipsychotic initiation waiting for fasting labs in acute situations 1. In patients with severe agitation, psychosis, or acute mania requiring immediate treatment, start the antipsychotic on Day 1 while simultaneously ordering baseline labs, then add results to the medical record once available 1. The priority is rapid symptom control; baseline labs can be obtained within the first few days of treatment 1.

Do not assume "normal" baseline labs mean the patient is safe from metabolic complications 1. Antipsychotics—particularly olanzapine and clozapine—can cause dramatic metabolic changes even in patients with initially normal values, which is why the follow-up monitoring schedule is equally critical 1.

Do not skip baseline documentation of pre-existing abnormal movements 1, 3. Before starting any antipsychotic, document any dystonia, tremor, or other movement abnormalities to prevent later misattribution of these findings to medication-induced tardive dyskinesia 1, 3.

Do not use random glucose as a substitute for fasting glucose without follow-up 1. If you cannot obtain a fasting sample initially, a random glucose serves as an acceptable screening measure, but if the random value is abnormal, prioritize obtaining a fasting measure subsequently 1.

Real-World Implementation

The 2018 Canadian population study found that only 17% of antipsychotic-naïve children received baseline laboratory testing, and less than 5% received lipid or glucose testing 4. This represents a massive gap between guideline recommendations and actual practice. The consequences of this monitoring failure include undetected diabetes, dyslipidemia, and preventable cardiovascular morbidity 4.

In elderly patients, baseline labs are particularly critical because this population has heightened vulnerability to metabolic and cardiovascular complications from antipsychotics 5. For patients with pre-existing diabetes, dyslipidemia, or obesity, consider adjunctive metformin prophylaxis when starting olanzapine or clozapine, which requires baseline renal function assessment 1, 2.

Adjunctive Metformin Consideration

When starting olanzapine or clozapine in patients with poor cardiometabolic profiles, consider adjunctive metformin 1:

• Before starting metformin: Assess renal function and avoid in renal failure 1
• Dosing: Start 500 mg once daily, increase by 500 mg every 2 weeks up to 1 g twice daily 1
• Monitoring: Annual liver function, HbA1c, renal function, and vitamin B12 1